With the development of wireless network and satellite communications, electronic products are trending toward the need for higher speed, frequency and larger capacity for the transmission of voice, video and data. In addition, as these electronic products become thinner and smaller, electrical circuit boards tend to increase in complexity, density and multi-layer stratification.
In order to maintain the high rate of transmission and signal integrity, printed circuit board (PCB) have a need for materials with low dielectric constant (Dk) and low dielectric loss (sometimes also called loss factor or dissipation factor, Df) thereby resulting in lower signal loss.
The current use of polyphenylene oxide, cyanate ester glue or modified epoxy glue in making prepregs are only able to produce laminates with glue content of 50-60% and Dk values of not less than 3.2. As such, these materials are unable to meet the high speed and signal transmission requirements. Chinese Patent Application Nos. 201210144675.4 and 201310476142.0 disclose mixing polytetrafluoroethylene (PTFE) powder and polyphenylene ether powder, and ball milling the same in a mixer cavity at 285° C. and compression molded to form a dielectric material layer. Fiberglass cloth material can be impregnated and sintered with PTFE resin to produce a prepreg, and bonded with copper foil, metal substrate, the compression molded dielectric material layer, and the prepreg in that order to form a multi-layer laminate material. The techniques disclosed in these applications are complex, cost prohibitive, and have difficulties associated with controlling the thickness and uniformity of the resulting multi-layer laminate material. Additionally, the appearance of the multi-layer laminate material is not smooth and therefore difficult to incorporate into PCB's that have multiple layers.
U.S. Pat. No. 2,539,329 discloses the use of pre-treating PTFE coated fiberglass at 205° C., followed by rolling and impregnating to improve the “mud cracks” of the PTFE coating. This method has the challenge in that the original coating layer can peel when it is re-dipped, and that it is difficult to laminate at temperatures below 250° C.